Isaiah 40:5

But when he took on flesh, he took on the universal logos of flesh. For he triumphed over the powers of all flesh in the flesh, and thus he came to the aid of all flesh, as is said in Isaiah, "all flesh will see …

(Verse 3 onwards) The voice of one crying in the wilderness: Prepare the way of the Lord, make straight in the desert a highway for our God. Every valley shall be lifted up, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain. And the glory of the Lord shall be revealed, and all flesh shall see it together: for the mouth of the Lord has spoken it. LXX: The voice of one crying in the wilderness: Prepare the way of the Lord, make straight the paths of our God. Every valley shall be filled, and every mountain and hill shall be brought low; and the crooked shall be made straight, and the rough ways shall be made smooth. And the glory of the Lord shall be revealed; and all flesh shall see the salvation of God, for the Lord has spoken. When the scribes and Pharisees and Jewish leaders heard John preaching in the wilderness and baptizing with a baptism of repentance, they sent messengers to ask him if he was the Christ, or Elijah, or a prophet. And when he answered that he was none of these, they asked him again, 'Then who are you?' So that we may give an answer to those who sent us. What do you say about yourself? And he answered: I am the voice of one crying out in the wilderness: 'Prepare the way of the Lord, as Isaiah the Prophet said (John 1:22-23)'. […]

And this is the Lord of glory, and we too have come to know his glory. However, those of old did not see it when he showed himself during the dispensation in which he was made man, equal to God the Father in strength, operation and glory, bearing all things by the word of his power and with great tranquillity performing godly works, enhancing creation, raising the dead and performing other deeds of wonder effortlessly. For the glory of the Lord appeared, and all flesh saw the salvation of God, that is, of the Father. For he has sent us his Son from heaven to salvation and redemption. For the law brings no one to perfection, for the sacrifices in prefigurative form were unable to deal with sin. But we have been perfected in Christ and reconciled from every fault as we have been honored with the spirit of sonship.

The one who has made these declarations, he says, is incapable of deceit. As for me, I am greatly astonished at those who think that the prophet has made these prophecies on the subject of the return from Babylon; for they should have considered that …

"And all flesh shall see the salvation of God." Because by "all flesh" is meant every person, not every person was able to see the salvation of God, namely Christ, in this life. Where then does the prophet direct the eye of prophecy in this statement except to the day of the last judgment? When, with the heavens opened, angels ministering, apostles seated alongside, Christ shall appear on the throne of His majesty, all—both the elect and the reprobate alike—will see Him, so that the just may rejoice without end in the gift of recompense, and the unjust may groan perpetually in the vengeance of punishment.